Aqueous alkali metal halogenite compositions are well known for use in the textile industry wherein the halogenite, especially sodium chlorite, is a source of chlorine dioxide gas, a strong bleachant. Below about pH 9.0, there is a sufficient concentration of H.sup.+ ions to commence conversion of the chlorite ion to chlorine dioxide, especially at elevated temperatures. As the concentration of chlorine dioxide in the aqueous solution increases, aqueous alkali metal halogenite compositions become more acidic and the rate of conversion increases.
In the paper industry, sodium chlorite has been used to prevent mold and slime growth in paper mill "white" water, as disclosed in U.S. Patent 3,046,185 to Buonanno.
Applicant has found that alkali metal halogenite solutions, especially sodium chlorite solutions, are suitable for use in household and janitorial cleaning chores, for example, cleaning of tiles, porcelain surfaces, and drains.
For such compositions, especially for compositions for household use, the inclusion of a colorant is preferred. The colorant provides a pleasing hue to the consumer, and makes the composition visible when applied to the work surface being cleaned. In some instances the colorant is an indicator that the product composition has been exhausted.
It has been observed, however, that many colorants, including those often used in household cleaning products, are not stable in the alkali metal halogenite compositions herein disclosed. Instability of the colorant is manifest by the formation of chlorine dioxide gas within the composition, by loss of tinctorial value of the colorant, and lowering of composition pH. Concomitant with the production of chlorine dioxide is the loss of the alkali metal halogenite. Moreover, chlorine dioxide odor is unpleasant and is detectable by the user of the composition when present even in trace concentrations.
It has been found that for many colorants that are otherwise unstable in aqueous alkali metal halogenite compositions, inclusion can be successfully achieved by successfully stabilizing the system with alkali metal salts of carbonates, borates, and mixtures thereof.
Accordingly, it is an object of the present invention to provide a cleaning composition comprising an aqueous alkali metal halogenite solution containing therein a colorant that retains its tinctorial value.
It is a further and primary object of the present invention to provide such compositions wherein the included colorant does not react appreciably with the sodium chlorite to release in excess of trace amounts of chlorine dioxide gas, at the pH of the composition.
These and other objects and advantages of the present invention will be more readily understood upon reading the detailed disclosure of the invention, a summary of which follows.